The invention relates to a locking apparatus with tumbler for safety doors.
Together with safety doors and safety fences, locking apparatuses are commonly used for safeguarding machines and installations, from which a risk emanates in operation, against unauthorized access. Start-up of such machines should only be allowed when the locking apparatus issues a “door closed” signal. In addition, renewed access to the machines should only be permitted when the machine no longer poses any risk. This is achieved by means of a so-called tumbler, i.e. the locking apparatus is not released until there is a stop signal or a similar signal from the machine or machine controller.
WO 95/06323 A1 discloses a locking apparatus where the tumbler is realized by means of a longitudinally displaceable ram in the frame part, said ram securing a ratchet wheel in a defined state. The locking of the safety door can be brought about by an actuator in the form of a key, which is fastened on the door part and is inserted into a receptacle on the frame part. The actuator rotates the ratchet wheel such that the ram is able to latch into an indentation of the ratchet wheel caused by the force of a spring. Removal of the key from the receptacle is prevented in this way. For the controlled release of the key once the machine has stopped, the ram is realized as the anchor part of a solenoid valve such that when the solenoid valve is supplied with current, the ram is transferred by the anchor lift out of the latching position into a release position. The key can then be removed out of the receptacle. In the case of this known locking apparatus, the ratchet wheel is arranged in a first housing part which can be combined in different positions with a second housing part, the ram sitting in the second housing part. As a result, the door part and the frame part can be used in different assembly positions in relation to each other.
The known locking apparatus, however, requires really small assembly tolerances. The door part and the frame part have to be aligned precisely with respect to each other so that the key is able to engage in the receptacle of the frame part. The small assembly tolerances result from the fact that the actuator has to be held securely in the receptacle. On the other hand, manipulation of the locking apparatus, for instance by inserting an insulated metal bolt in place of the actuator, is to be counteracted. Consequently, the actuators of such locking apparatuses, as a rule, are complexly formed parts which cooperate with precisely matched ratchet wheels. As a rule, the receptacle for the actuator is also extremely tight. This results in the small assembly tolerances.
Small assembly tolerances make the assembly difficult. They can cause problems over time if the safety door sinks on account of its weight. DE 10 2005 057 108 A1, consequently, discloses a locking apparatus with a door part and a frame part which allow larger assembly tolerances. The door part has an actuator which can engage in a relatively large pocket on the frame part. A blocking member for blocking the actuator is arranged on the door part. Said known locking apparatus, however, does not provide any different assembly positions for the door part and the frame part in relation to each other and, consequently, is less flexible to use.